A primary objective of the proposed center is to establish a laboratory for ongoing optimization of a comprehensive smoking cessation intervention. Our definition of intervention optimization is: Employing scientific theory and efficient methodology to produce an evidence-based intervention that represents the maximal improvement in effectiveness, translatability and/or cost-effectiveness over currently available interventions. In the proposed center we plan to approach intervention optimization by using an innovative optimization cycle framework inspired by engineering methods. The optimization cycle is an extension and elaboration of the Multiphase Optimization Strategy (MOST), a phased experimental approach to intervention development and optimization developed by Collins, Murphy, Nair, and Strecher1 2. Potential advantages of using the, optimization cycle framework include: It is a systematic and principled approach, and therefore is the fastest way, in the long run, to an appreciably improved smoking cessation intervention; it provides a straightforward way of testing hypotheses about potential new intervention components or changes to existing components; it provides a natural way of including cost information in the basis for decision making about intervention development; and it will help contribute to the building of a coherent cumulative base of scientific knowledge about smoking cessation. The Intervention Optimization Core has four Specific Aims: (1) to serve as an intellectual resource to the center, providing ongoing input on the innovative optimization cycle framework and related statistical and methodological consultation as needed; (2) to conduct original methodological work to refine the optimization cycle approach, based on issues that arise in the course of the proposed optimization cycle; (3) to disseminate information about the optimization cycle approach to drug abuse prevention and treatment scientists, using the work of the proposed center as an illustration; and (4) to conduct exploratory analyses in preparation for a second optimization cycle, in collaboration with the Methods Core.